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About "Light", need better understanding of it.

  1. Feb 14, 2015 #1
    Is there different types of light/particles of light? because all of these lights are different how it works, laser light, light from flash light, sun light. Why does flash light only illuminate only less area/more area depending on how much volts the battery is and a sun illuminates a whole earth and stays on illuminating? What is darkness in a room with light off and what is illumination in a room with light on?
  2. jcsd
  3. Feb 14, 2015 #2
    Are you really asking why a flashlight isn't like a star?

    Light are photons of a certain wave length. Both a star like our sun and a flashlight generate them, only one of them generates a lot more of them.
    So light has two properties. The number of photons and their energy/wave length/frequency.

    What is darkness? No photons hitting your retina and thus no nerve signal to your brain.
  4. Feb 14, 2015 #3
    If you're in a room where nothing moves then you will hear no sound, nothing will hit your ear drum. The harder you hit something, meaning the more energy you put into it the more that will reach your ear.
  5. Feb 14, 2015 #4


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    Visible light is but one small section of the larger electromagnetic spectrum. Light, and everything else on this spectrum, is first and foremost an electromagnetic wave. This EM wave interacts with matter via 'photons', which we call the particle of light. (But in reality they are nothing like a particle in the classical sense) The only difference between, say, radio waves and visible light, is that radio waves have a much longer wavelength and much smaller energy per photon than visible light.

    Creating light requires energy. A flashlight only puts out a small amount of energy per second in the form of light, while the Sun puts out an enormous amount thanks to its temperature and sheer size. (Energy per second is known as 'power') The more power your flashlight puts out, the brighter the light is. A flashlight's energy source is its battery, which only holds a small amount compared to the Sun. The Sun simply has a much, MUCH larger reserve of energy in the form of gravitational potential energy and nuclear fusion. So while your flashlight can only stay lit up for a few hours, maybe a day or two if you have a newer LED flashlight, the Sun can shine for billions of years.
  6. Feb 14, 2015 #5


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    What you are writing there are light sources, not the light itself. Some basic properties of light have been pointed out by Drakkith. While those lightsources emits different light characteristics (e.g. power, spectrum, directionality, coherence) because the underlying physics behind the generation is different as well.
  7. Feb 15, 2015 #6
    Thank you all for the answers! :)
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